Tin - Sn, 50

Tin has a melting point of 231.9681°C, boiling point of 2270°C, specific gravity (gray) of 5.75 or (white) 7.31, with a valence of 2 or 4. Tin is a malleable silvery-white metal which takes a high polish. It possesses a highly crystalline structure and is moderately ductile. When a bar of tin is bent, the crystals break, producing a characteristic 'tin cry'. Two or three allotropic forms of tin exist. Gray or a tin has a cubic structure. Upon warming, at 13.2°C gray tin changes to white or b tin, which has a tetragonal structure. This transition from the a to the b form is termed the tin pest. A g form may exist between 161°C and the melting point. When tin is cooled below 13.2°C, it slowly changes from the white form to the gray form, although the transition is affected by impurities such as zinc or aluminum and can be prevented if small amounts of bismuth or antimony are present. Tin is resistant to attack by sea, distilled, or soft tap water, but it will corrode in strong acids, alkalis, and acid salts. The presence of oxygen in a solution accelerates the rate of corrosion.

Tin is used to coat other metals to prevent corrosion. Tin plate over steel is use to make cans for food. Some of the important alloys of tin are soft solder, fusible metal, type metal, bronze, pewter, Babbitt metal, bell metal, die casting alloy, White metal, and phosphor bronze. The chloride SnCl·H₂O is used as a reducing agent and as a mordant for printing calico. Tin salts may be sprayed onto glass to produce electrically conductive coatings. Molten tin is used to float molten glass to produce window glass. Crystalline tin-niobium alloys are superconductive at very low temperatures.